1. Technical Field
The present invention relates to a target image detection device for detecting a target image from an original image, a controlling method of the same, a control program and a recording medium recorded with the program, and an electronic apparatus equipped with the target image detection device.
2. Related Art
Conventionally, needs for automatically recognizing a photographing target or a displaying target to provide an easy-to-use user interface or to automatically acquire an optimum image are increasing in an imaging device, a display device, and the like. One example of such needs includes a function of detecting a face of a person and making an adjustment such that an optimum focus and exposure are obtained on the detected face, or recognizing a character and automatically having a region of the recognized character as a target of OCR (Optical Character Recognition).
Generally, in order to realize such a function, an advanced image processing is required, and an enormous amount of calculation is required. The above-described function generally requires real-time performance, and thus high-speed processing is necessary. It is thus often difficult to realize such a function in an incorporating device where processing ability, power consumption, and cost are restricted such as a digital camera or a mobile communication terminal.
Various methods for increasing the speed of processing have been proposed for such a problem. For instance, in an image processing device described in Japanese Unexamined Patent Publication No. 2007-135115, reduced images are sequentially template matched in an order a resolution sequentially changes in a step-wise manner, a region in which a specific subject is photographed is detected, and the processing is interrupted after the detection to increase the speed of the processing. Furthermore, in a face detection method described in Japanese Unexamined Patent Publication No. 2006-301847, the faces are detected in order from large faces, and detection is subsequently continued excluding the region where a face is already detected from the detecting target region. The detecting target region thus can be reduced every time a face is detected, and the speed of processing can be increased.